1. Field of the Invention
The present invention relates to an image-forming system such as a printer connected to a host device such as a host computer and an image-forming program.
2. Description of Related Art
An image-forming system according to a related art has a restriction of memory capacity, and therefore, divides image data into a plurality of bands each containing divided bitmap data. The bands of divided bitmap data are successively loaded into, for example, band memories 1 and 2. For example, first and second bands are loaded into the band memories 1 and 2, and thereafter, the first band is transferred from the band memory 1 to a print engine. Thereafter, a third band is loaded into the band memory 1 by overwriting the first band existing in the band memory 1. The first band transferred to the print engine is printed on a sheet of paper. All the bands are transferred to the print engine to be printed like wise manner.
The image-forming system may read a plurality of image data pieces, enlarge or reduce the read data pieces, combine the enlarged or reduced data pieces into one, and print the combined data piece on a single sheet of paper. This process is called an N-up process. The N-up or the like process needs a large processing capacity to limit the processing speed of the image-forming system.
FIG. 7 explains the N-up process, in particular, a 4-up process that conducts 4-in-1 printing. In FIG. 7, four image data pieces 101, 103, 105, and 107 are scanned and read one by one, are reduced, and are stored in a memory. The reduced data pieces 101, 103, 105, and 107 are combined into one data piece having a final image size of A4 (Japanese Industrial Standard). The final data piece is stored in a memory region whose size corresponds to the size of A4 paper. The combined data piece is divided into bands 1 to 7 each containing divided bitmap data. The bands are sequentially transferred to a print engine and are printed as mentioned above.
Rearranging the final image in the memory region into bands increases the number of processes and delays a processing speed.
In FIG. 7, a data end 109 of the image is in the middle of the band 7 as a last one of the divided bands. It is necessary, therefore, to memorize the location of the data end 109 in the band 7 so that nothing is printed after the data end 109. This further increases the number of processes and delays a processing time.
To increase a processing speed, there is a technique to change the height of one band. This technique, however, is not effective for the N-up process or when a data end is in the middle of a band because the above-mentioned data rearranging process and data end memorizing process are needed in such a case.
Changing the heights of some bands causes an incident that a band of higher height must be loaded into a band memory within a short period in which a band of lower height is output to a print engine. Then, the band of higher height is not completely loaded into the band memory within the period, to cause a print overrun error. (Refer to Japanese Unexamined Patent Application Publications No. 2000-301781, No. 2001-171185, No. 2003-80771, and No. 2003-72161.)